This invention relates to cutting tools and, more particularly, to an improved knife having a blade that is easily removable and replaceable.
There have previously been devised many types of hand-held cutting tools for use by craftsmen such as draftsmen, artists, photographers, etc. The majority of such cutting tools employ a small blade that is rigidly mounted at the end of the tool. The blade is generally mounted in removable fashion to facilitate the changing thereof, but it must be secure enough to minimize the chance of its slipping or dropping out. Typically, the end of the tool is provided with a slit into which the blade is seated and a screw-on collet compresses the slit so that the blade is grasped. This mounting arrangement requires significant time and trouble for loosening, removal, replacement, and tightening of the collet whenever the blade is to be changed. Also, the torque on the blade caused by twisting motion during use can tend to cause unwanted looseness of the collet. An example of this arrangement is shown in U.S. Pat. No. 2,569,286.
In U.S. Pat. No. 2,619,724 there is disclosed a technique wherein a blade-holding chuck is controlled by a threaded mechanism in conjunction with a spring at the rear end of the knife. A user can replace a blade by appropriate loosening or tightening of the mechanism which controls the blade-holding chuck. This technique may be somewhat faster than the conventional collet arrangement described above, but still involves screwing and unscrewing operations. The degree of tightness and rigidity is a function of human judgement and finger strength and thereby subject to error. Also, precise manufacturing tolerances of the screwing mechanism and provision for and assembly of the spring are factors in manufacturing cost and maintenance.
It is an object of the present invention to provide an improved knife wherein blade removal and replacement is extremely simple, blade rigidity is not a function of human judgement, and economies of manufacture and maintenance are realized.